A compound word is typically created when two or more words are joined together. In this way, compound words by their very definition form a “new” word, with its own meaning, linguistic part of speech and given discourse neutral prominence pattern. For example, a two-word compound word may have default prominence on the left word in the compound word.
Ensuring that the compound word prominence pattern is correct in text-to-speech (“TTS”) synthesis is important, as listeners are sensitive to this, and it has a bearing on the perceived quality of the synthesized utterance. This prominence should be the same no matter the orthographic form of the compound word, for example, if it is “fire fly”, “fire-fly” or “firefly”.
It is notoriously hard to define what constitutes a compound word. Clearly the new compound word will function as a “new” word, and have its own meaning and grammatical part of speech, but the conditions under which this compounding occurs are ill-defined. For example, it is not sufficient to assume that all noun-noun words co-occurring together in text are noun-noun compound words. Most TTS systems handle compounds words by simple dictionary methods only, which has limited effectiveness given the rich compositionality of compound word forms.